West Midlands Training Course/MSc in Clinical Biochemistry

Course Assessment – Spring 2008

Short Answer Questions. Answer all questions. Time allowed 1 hour

1. What is the absorbance of a 1cm pathlength of acetonitrile at 200nm when the percentage transmission is 80%? 10 marks

2. Define 1 unit of enzyme activity 10 marks

3. List five biochemical abnormalities associated with rhabdomyolysis. 2marks each

4. A 70 kg man with severe hypomagnesaemia requires 24 mmol of magnesium intravenously.

a. What volume of solution containing 0.48g/2mL of anhydrous magnesium sulphate would be needed ? (Atomic Weights Mg = 24, S=32) 5 marks

b. What is the final calculated osmolarity of the solution if this volume is added to 500 mL of 0.9% w/v sodium chloride? 5 marks

5. A new screening test has been developed to detect a tumour with a prevalence of 1 in 5000 of the population. It has a diagnostic sensitivity of 95% and a specificity of 97%.

a. Calculate the diagnostic efficiency of the test 5 marks

b. Calculate the negative predictive value of the test 5 marks

6. A 22 year old painter and decorator presented to his GP with a 2 week history of lethargy, malaise, headaches, nausea and cramping abdominal pain. Blood results were as follows

Na 140 mmol/L
K 4.2 mmol/L
U 5.6 mmol/L
Cre 103 umol/L
Alb 40 g/L
ALT 24 U/L
ALP 88 U/L
Bili 6 umol/L
Hb 9.4 g/L
MCV 92 fl
WCC 13.2 x109 L-1
Platelets 231 x109 L-1

Basophilic stippling of erythrocytes was noted on the blood film.

a. What is the most likely diagnosis? 4 marks

b. What is the mechanism behind the abnormal blood results? 3 marks

c. What management/treatment options are available? 3 marks

7. A paper describing the use of a new tumour marker included the following data relating to the concentrations of histologically proven disease:-

Number of diseased patients (n) = 110
Mean concentration of tumour marker = 80 U/L
Standard error of mean = 5.5

a. Calculate the standard deviation of the mean 5 marks

b. If the reference interval for the tumour marker in non-diseased subjects is 10-15 U/L what can you conclude about the distribution of data in the diseased patients in this study? 5 marks

8. One serum and one urine sample collected from a patient for the measurement of creatinine clearance were each assayed 10 times with the following results:-

Urine Creatinine Serum Creatinine
mmol/L umol/L

11.1 102
11.5 108
11.9 107
10.9 112
12.1 103
11.2 105
11.8 109
11.7 114
11.6 110
12.1 100
The urine was a 24 hour collection and had a volume of 1250 mL.
What is the analytical imprecision in the creatinine clearance determination?
10 marks

9. Match the following disease states with their biochemical/other characteristics in adults

a. Carcinoid disease
b. Phaeochromocytoma
c. Gastrinoma
d. VIPoma
e. Somatostatinoma

Biochemical/Other Characteristics

B1. Fasting blood sugar of greater than 9.0mmol/L on 2 occasions, raised faecal fats
B2 Pancreatic tumour with achlorhydria
B3 Pancreatic tumour often associated with MEN1
B4 Elevated urine 3-hydroxy 4-methoxy mandelic acid output
B5 Elevated urine urine 5 –hydroxyindol acetic acid output and raised plasma chromogranin A
B6 Raised plasma glucagon 2 marks each

10. A 54 year old man with chronic renal failure is admitted to AE with chest pain. ECG changes are suggestive of a possible MI but are not conclusive. Troponin T at 12 hours post onset of chest pain = 0.12 ug/L. The renal registrar phones wanting to know if the patient has had an MI.

a. What do you tell him?

b. What further investigations may help?

5 marks each

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